Topological Surface State of Bi₂Se₃ Modified by Adsorption of Organic Donor Molecule Tetrathianaphthacene

Abstract

Topological insulators (TIs) are expected to realize new spintronic devices with low dissipative electrical transport. Organic molecule/TI interfaces have been investigated to explore the potential of multifunctional organic molecules for TI devices. However, there is no unified understanding of the interfacial electronic structure. The electronic structure of the molecular side must be examined to fully understand the phenomena at the interface. Thus, this paper reports the investigation of the interface between the electron‐donating organic molecule tetrathianaphthacene (TTN) and prototypical TI Bi2Se3 by ultraviolet photoemission spectroscopy (UPS), X‐ray photoemission spectroscopy (XPS), and angle‐resolved photoemission spectroscopy (ARPES). The deformation of the Fermi surface of the topological surface states as well as the formation of a 2D electron gas state (2DEG) at the interface occurs upon TTN deposition onto Bi2Se3. Confinement of the 2DEG into the surface arises from band‐bending accompanied by electron donation from TTNs to Bi2Se3 according to XPS and UPS. The knowledge obtained in this work shed new light on the understanding of the electronic structure of organic molecules/TI interfaces and open the door to the TI applications via modification by electronic functional organic molecules.

Topological Surface State of Bi2Se3 Modified by Physisorption of n‐Alkane

“…In the case of TTN/Bi 2 Se 3 , the TSS energy was greatly reduced by electron donation from TTN to Bi 2 Se 3 , resulting in the formation of a two-dimensional (2D) electron system confined at the TTN/ Bi 2 Se 3 interface. [10] Accordingly, ARPES revealed a hexagonalshaped Fermi surface of the 2D electrons inside the Fermi surface of the TSS. No Fermi surface of the confined 2D surface electrons was observed in the case of TTC/Bi 2 Se 3 , as shown in Because the 20 Å TTC thick molecular layer corresponds to more than two layers, it is thicker than the escape depth of photoelectrons measured by ARPES [23] and the observed intensity is drastically reduced.…”

“…The same trend is observed at the TTN/Bi 2 Se 3 interface, where the largest peak shift is observed at the core-level of Se 3p. [10] This is because among these Bi 2 Se 3 orbitals, the Se 3p orbital has the largest spatial distribution near the surface. Thus, the Se 3p orbital largely contributes to the screening effect against changes in the surface potential when molecules are adsorbed on the Bi 2 Se 3 surface.…”

“…The energy shift in the valence band of Bi 2 Se 3 observed at the TTC/Bi 2 Se 3 interface was approximately 60 meV, which was much smaller than the band bending of over 300 meV observed for TTN/Bi 2 Se 3 . [10] Therefore, the formation of 2D electron systems confined at the interface, such as those found in TTN/Bi 2 Se 3 , was not observed.…”

“…Furthermore, a recent study on the change in the TSS of Bi 2 Se 3 by adsorption of tetrathianaphthacene (TTN), a typical electron-donating molecule, has been reported. [10] The adsorption of TTN causes a large shift of DP toward a higher binding energy due to electron donation from TTN, resulting in a large deformation of the Fermi surface in the TSS. Previous studies have shown that the adsorption of electron-accepting or electron-donating organic molecules, often accompanied by electron transfer, is useful for controlling the TSS of TI.…”

A High‐Performance Self‐Powered UV‐Visible‐Infrared Broadband Photodetector Based on a Solution‐Processed Bi2Se3/Se Nanorods Heterojunction

“…The synthetic Bi 2 Se 3 in the solution has a flaky appearance owing to its special hexagonal layered structure. [ 34 ] At last, only a few of Bi 2 Se 3 synthesize on the surface of Se NRs to form Bi 2 Se 3 /Se NRs heterojunction, the others generate in the solution and form Bi 2 Se 3 nanosheets. Accordingly, a mixture of NRs and nanosheets are obtained, as shown in route 2.…”